Deputy Attorney General Rod Rosenstein has appointed former FBI Director Robert Mueller to serve as special counsel to oversee the previously confirmed investigation of Russian efforts to influential the 2016 Presidential election and related matters.

“I have determined that a Special Counsel is necessary in order for the American people to have full confidence in the outcome,” Rosenstein said in a statement.

The letter announcing the appointment reads that Mueller is authorized to investigate “any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump; and…any matters that arose or may arise directly from the investigation.”

The appointment comes as numerous Democratic lawmakers have called for a special counsel, colloquially known as a special prosecutor. Such calls increased in recent days after Mr. Trump fired FBI Director James Comey. On Tuesday, it was revealed the Comey had written a memo alleging that Mr. Trump had asked him to back off from investigation former National Security Adviser Michael Flynn.